Third Draft

breed [predators predator]
breed [shells shell]
turtles-own [health]

to setup
  clear-all
  setup-patches
  setup-predators
  setup-shells
  reset-ticks
end 

to go
  if ticks >= 1000000 [ stop ]
  move-predators
  move-shells
  reproduce
  check-death
  ask predators [
    set health health - 1
    catch-shells
    reproduce
  ]
  ask shells [
    set health health - 1
    eat-grass
    reproduce
  ]
  tick
end 

to setup-patches
  ask patches [ set pcolor blue ]
end 

to setup-predators
  create-predators number[ set health 100 setxy random-xcor random-ycor set shape "fish" set color orange fd random 10 ]
end 

to setup-shells
  create-shells number[ set health 100 setxy random-xcor random-ycor set color white set shape "dot" fd random 10 ]
end 

to move-predators
  ask predators [
    right random 360
    forward 1
    rt random 20
    lt random 20
    set health health - 1
  ]
end 

to move-shells
   ask shells [
    right random 160
    forward 1
    rt random 20
    lt random 20
    set health health - 1
   ]
  ifelse pcolor = blue
  [ eat-grass ]
  [ get-zapped ]
end 

to reproduce
  ask turtles [
  if health > 50 [
    set health health - 5
    hatch 1 [ set health 50 ]
  ]
]
end 

to check-death
  ask turtles [
    if health <= 0 [ die ]
  ]
end 

to eat-grass
  ask shells [
    if pcolor = blue [
      set pcolor green
      set health health + 10
    ]
  ]
  ask shells [
    if pcolor = green [
      get-zapped
    ]
  ]
  ifelse show-health?
  [ set label health ]
  [ set label "" ]
end 

to catch-shells
  let prey one-of shells-here
  if prey != nobody
    [ ask prey [ die ]
       set health health + 1000 ]
end 

to get-zapped
  set health health - 10
end